This invention relates to a motor/generator provided with two or more rotors driven by a compound current.
JP1999-275826A published by the Japanese Patent Office in 1999 discloses a motor/generator driven by a compound current. This motor/generator provides a cylindrical inner rotor and a hollow outer rotor disposed coaxially with a hollow cylindrical stator, there being a predetermined gap between the inside and outside of the stator.
However, in this conventional motor/generator, even if linear voltage control is performed by an inverter, the maximum phase voltage of each phase can only be half of the alternating current voltage supplied from the inverter, and the utilization factor of the voltage is low. Moreover, as the phase voltage cannot be increased even if the current utility factor is improved by using a compound current, the required apparent power becomes small.
If the alternating current voltage is increased by using a chopper, the alternating current voltage is high and the loss of the inverter increases. Furthermore, the number of power devices forming the inverter increased, the number of electronic parts, such as drivers, increased as a result, and this leads to restriction of layout flexibility and increased cost.
It is therefore an object of this invention to provide a motor/generator which solves the above-mentioned problem. The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
To achieve the above objects, this invention provides a motor/generator comprising a stator in which plural coils are disposed, rotors that are coaxially arranged with the stator and rotate by magnetic force generated by the coils, a device that generates a compound current from a direct current base on a command voltage to supply to the coils, and a controller functioning to calculate a neutral point potential and calculate the command voltage with reference to the neutral point potential.